1. Field of the Invention
The invention relates to a power semiconductor module with a plastic housing into which a substrate is inserted as a housing base. The substrate contains a ceramic plate provided with a metallization layer on top and bottom sides. The metallization layer on the top side of the ceramic plate faces an interior of the housing and is patterned in order to form interconnects. The power semiconductor module is equipped with semiconductor components and connecting elements, and in which terminal elements for external terminals are introduced.
Such power semiconductor modules have been known for a long time. In the case of these power semiconductor modules, the terminal elements for the external terminals are disposed in the plastic housing. In this case, the terminal elements, which are composed of copper as a rule, are injection-molded into the plastic housing. However, plastic has the property of shrinking when it cools, in other words after the injection molding. The result of this is that the terminal elements are not, as a rule, anchored fixedly in the plastic. Wires are bonded onto the terminal elements in the interior of the housing, the other end of which wires is bonded onto the semiconductor components. These wires are composed of aluminum as a rule. By virtue of the fact that the plastic shrinks after the injection molding, however, it can happen that, owing to the poor mechanical fixing of the terminal elements in the plastic housing, the bond present in the interior of the housing may become detached. This leads to the failure of the power semiconductor module.
It is accordingly an object of the invention to provide a power semiconductor module with a ceramic substrate that overcomes the above-mentioned disadvantages of the prior art devices of this general type, which exhibits very good mechanical fixing of the terminal elements, with the result that the above-mentioned problems do not arise. Furthermore, the object of the present invention is to further simplify the method for producing the plastic housing.
With the foregoing and other objects in view there is provided, in accordance with the invention, a power semiconductor module, including semiconductor components and connecting elements.
A plastic housing has a frame and a cover. The frame is formed with an interior and openings surrounding the interior. The openings have a flat side remote from the interior and an inner side adjacent the interior.
A substrate disposed in the plastic housing defines a housing base of the plastic housing. The substrate contains a ceramic plate having a top side and a bottom side with a top metallization layer disposed on the top side and a bottom metallization layer disposed on the bottom side. The top metallization layer facing the interior of the frame is patterned in order to form conductive interconnects and is equipped for receiving the semiconductor components and the connecting elements.
Terminal elements in the plastic housing for providing external terminals have a flat rear side, a bottom side, two lateral sides and a front side with lugs. The terminal elements in the region of the lugs are press-fitted into the openings in the frame. The rear side of the terminal elements bears on the flat side of the openings. The lugs press against the inner side of the openings for fixing the terminal elements in position.
The connecting elements are bonded to the terminal elements and to the semiconductor components.
This object is achieved according to the invention by virtue of the fact that the terminal elements are press-fitted into openings in the plastic housing.
As a result of this measure, the metal parts are fixed into the plastic housing by a relatively simple method. In particular, this method does not need a separate injection mold into which the terminal elements are placed before each injection-molding process and subsequently encapsulated by the injection molding.
Furthermore, as a result of the terminal elements being press-fitted into the openings in the plastic housing, the elements are anchored considerably better therein, thereby enabling reliable bonds in the interior of the housing.
The lugs of the terminal elements are preferably configured as barbs, with the result that the terminal elements are guided tightly in the openings and secured from withdrawal. It is also conceivable for the terminal elements to be provided with offsets that fix the terminal elements in the openings.
The terminal elements expediently have regions in the interior of the housing which run approximately parallel to the housing base. This considerably facilitates the bonding process.
The substrate is covered, within the housing, with a potting compound that serves to encapsulate the substrate in a moisture-tight manner.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a power semiconductor module with a ceramic substrate, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.